1. Field of the Invention
The present invention relates to a substrate processing apparatus which performs a substrate processing with a substrate being rotated.
2. Description of the Background Art
Substrate processing apparatuses which perform a substrate processing by rotating semiconductor substrates or glass substrates (hereinafter, referred to as “substrates”) and supplying the substrates with various processing solutions (including cleaning solution) have been conventionally used. In such a substrate processing apparatus, usually, a substrate is supported from a lower portion and a mechanism for supporting the substrate is connected to a rotation axis of a motor, to thereby rotate the substrate.
On the other hand, in order to achieve a high-level substrate processing by using a downsized apparatus at lower cost, a thin ring rotation mechanism has been proposed recently. Specifically, a rotation mechanism with no rotation axis which comprises a motor having a ring-shaped stationary part (stator) and a ring-shaped rotating part (rotor) has been proposed.
With recent upsizing of substrates and the necessity of high-speed rotation of the substrates in the processing, however, there arises some problems if a ring-shaped motor is manufactured with ordinary techniques. Specifically, it is necessary to upsize the ring-shaped motor with the upsizing of substrates and heat generation inside the motor ill affects bearing mechanisms such as a gaseous bearing and a rolling bearing of large diameters. As a result, the motor can not exercise its performance required for the substrate processing.